The present invention relates to a signaling method and a network element for a telecommunication network providing a virtual private network (VPN).
The VPN concept allows private traffic traditionally served by leased private lines to share the existing trunk capacity of the PSTN (Public Switched Telecommunication Network). This allows for a more efficient utilization of network resources and provides a number of benefits to both operators and users. Network costs can be more closely tied to actual usage. With private networks, the cost of inter-site traffic is tied to the maximum capacity required, not overall usage. VPN also allows for increased flexibility in configuring the network.
QSIG (unified international corporate network signaling standard) is an ISDN common channel signaling system designed for use in corporate networks. It was developed in an open forum for all major European PBX manufacturers. The name QSIG refers to signaling across the ISDN xe2x80x9cQxe2x80x9d reference point which is the logical signaling point between two PINXs. QSIG defines a set of protocols for the interaction of PINXs, so that common sets of services and features, with similar appearances, are available to users across private networks, including multi-site networks.
The original standards for QSIG were developed by the ECMA (European Computer Manufacturers Association). Later, these standards were used as a basis for the ETSI (European Telecommunications Standards Institute). The main standards covering the Basic Call Protocol are Layer 2 ETS 300 402-1 based on ITU-T Q.920 and Layer 3 ETS 300 172 (for the PSS1 signaling system) based on ISO/IEC 11572, or EN 301 060 (for the DSS1+ signaling system).
In addition thereto, a standard which covers the Core Generic Functional Protocol for supplementary services for private telecommunication networks has been developed by ISO (ISO/IEC 11582) and given the ETSI identification ETS 300 239. This is the core protocol that the individual supplementary services use to avail of the transport services of the underlying layers.
A VPN product provides QSIG interfaces for interconnecting remote PINXs (Private Integrated Services Network Exchanges) across the PSTN, either via a single exchange or via a number of exchanges in the network. Conceptionally, the entire exchange network is seen by the end PINXs as a simple transit network.
The transport of the QSIG signaling over the PSTN (e.g. ISDN network) is accomplished by xe2x80x9cenvelopingxe2x80x9d QSIG messages within ISUP (ISDN User Part) messages. This method enables common ISUP signaling links and associated bearers to be provisioned for VPN and non-VPN traffic for greater efficiency.
To be able to offer a true on-net call and to provide for the transparent transfer of QSIG messages over the PSTN from the VPN entry point to the VPN exit point (when the VPN extends over multiple exchanges), a technique called Application Transport Mechanism (APM) is used. This means that a call is set up over the PSTN to provide for the connection, and all associated QSIG data is transmitted along the call with the APM mechanism. The receiving end extracts the data and sends an identical message to the destination PINX. Thus, PINXs see the network as a dedicated private network with QSIG signaling.
Since there may be parts of the PSTN that do not support the signaling, or the destination subscriber is not capable of supporting the protocol, a method is defined in the ETSI specification EN 301 062-1 to drop the call to support only a basic call. When such a situation is detected, a so-called gateway function is performed and the necessary parts of the private network signaling are transformed to a PSTN signaling. This method is specified in such a way that the QSIG information is always carried with the call set up in the PSTN. If transparency is lost, i.e. the destination does not support QSIG, then the QSIG data is dropped from subsequent messages in a gateway function of the network after this condition is detected. Hence, the initial OSIG signalling leads to an increased load in the signaling network.
It is therefore an object of the present invention to provide a signaling method and network element for a telecommunication network providing a virtual private network, by means of which the signaling load in the telecommunication network can be decreased.
This object is achieved by a signaling method for a telecommunication network providing a virtual private network, said signaling method comprising the steps of:
determining a destination capability in response to the receipt of a connection request from a subscriber belonging to the virtual private network; and
deciding on the initiation of a virtual private network signaling in the call set-up, based on the determination result in said determination step.
Furthermore, the above object is achieved by a network element for initiating a signaling in a telecommunication network providing a virtual private network, the network element comprising:
determining means for determining a destination capability in response to the receipt of a connection request from a subscriber belonging to the virtual private network; and
signaling control means for deciding on the initiation of a virtual private network signaling in the call set-up, based on the determination result of said determining means.
Accordingly, a pre-defined signaling load decrease is enabled by checking the destination capability during the initiation of a set-up procedure in the originating point. If the destination is not able to support the signaling, the originating node performs a gateway function without initiating the VPN signaling in the call set-up. Since it is known that certain types of VPN members do not support the VPN signaling in the first place (e.g. mobile terminals, old PBXs (Private Branch Exchanges)), the load produced by the set-up signaling for these members can be reduced. Known standardized methods may still be used as a back-up for those nodes that can change to support the VPN signaling in the future (e.g. international VPN members).
Preferably, the destination capability may be determined on the basis of a private numbering plan which may be stored at the originating node. Alternatively, the private numbering plan may be stored in an IN (Intelligent Network) node located at the originating node of the connection request. In particular, the virtual private network signaling may not be initiated if the private numbering plan indicates a mobile subscriber as the destination of the call.
Preferably, the network element may be an originating node of the connection request. Particularly, the network element may be a network exchange.